The results of these simulations for the selected representative winter period from 16th — 31st July are shown in Figure 3. This graph shows the heating energy of the outlet air from the 16m2 PVT system simulated in TRNSYS compared with the required house heating as modelled using both IDA ICE and TRNSYS. Reasonable correlation is shown between the heating demand results for the house as simulated by IDA ICE and TRNSYS.

Figure 3 shows that on most days during the selected period the supplied PVT heating energy is in excess of the required house heating as modelled in both IDA ICE and TRNSYS. During the 4 day period where the required house heating is greater than that supplied by the PVT system it is expected that the indoor temperature would drop and the degree of this decrease can be seen in Figure 4.

The PVT system integrated into the house was modelled in TRNSYS to determine the resulting indoor zone temperatures when the heated outlet air from the PVT system was directed into the house. The PVT system operated on an input schedule and only delivered heating energy to the building during the colder months from May to August. The resulting indoor temperatures for the house with and without a PVT system are shown in comparison with the ambient air temperature in Figure 4. The running average temperatures for the house and ambient air were calculated by averaging the values over a 20 day period — 10 days before and 10 days after each time point.

Figure 4 illustrates that the heating energy supplied by the PVT system is effective in increasing the indoor air temperature of the well insulated house. The running averages show that the indoor temperature of the house with the PVT system is up to 8°C above the ambient running average temperature during the period from May to August and is also 3°C above the running temperature of the house without a PVT system.

The average running zone temperature presents a promising result in that the temperature does not drop below 20°C. However the simulated indoor house temperature results show that the indoor temperature can drop to a similar temperature level to the house without the PVT system, showing that there is very little heating input during this period. This was also shown in Figure 3. The temperature during this period can drop to 16°C overnight. Despite the thermal mass modelled in the house, the results showed greater than expected daily swings in internal building temperature. This shows that the coupling between the thermal mass and the indoor air could be improved. A method for doing this would be to increase the surface area of the thermal mass inside the zone by

adding thermally massive internal walls to the simulation model to facilitate the exchange of heat with the inside air.